We study the interactions between polymer-grafted nanoparticles immersed in a chemically identical polymer melt using a numerical implementation of polymer mean-field theory. We focus on the interpenetration width between the grafted and free chains and its relationship to the polymer-mediated interparticle interactions. To this end, we quantify the interpenetration width as a function of particle curvature, grafting density, and the relative molecular weights of the grafted and free chains. We show the onset of wetting and dewetting as a function of these quantities and explain our results through simple scaling arguments to include the effects of curvature. Subsequently, we show that the interparticle potentials correlate quantitatively with the trends displayed by the interpenetration widths.

We present experimental results for the glass transition behavior of polystyrene (PS) films on grafted PS layers of the same chemical identity as a function of film thickness. Our results suggest that the T g of PS films on brush substrates decreases with decreasing film thickness. The thickness dependence of T g was observed to be more pronounced for the films on the shorter brushes with the high grafting density. We propose a qualitative rationalization of the observations by invoking both interfacial energy considerations as well as by adapting the percolation model for the glass transition of polymer films.

Transgenic plant cell cultures offer a number of advantages over alternative host expression systems, but so far relatively low product concentrations have been achieved. In this study, transgenic rice cells are used in a two-compartment membrane bioreactor (CELLine 350, Integra Biosciences) for the production of recombinant alpha-1-antitrypsin (rAAT). Expression of rAAT is controlled by the rice alpha-amylase (RAmy3D) promoter, which is induced in the absence of sugar. The extracellular product is retained in the bioreactor's relatively small cell compartment, thereby increasing product concentration. Due to the packed nature of the cell aggregates in the cell compartment, a clarified product solution can be withdrawn from the bioreactor. Active rAAT reached levels of 100-247 mg/L (4-10% of the total extracellular protein) in the cell compartment at 5-6 days postinduction, and multiple inductions of the RAmy3D promoter were demonstrated.

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We model the self-assembly of a diblock copolymer thin film in contact with a random copolymer brush using self-consistent field theory employing a quenched distribution for the brush chains. We focus on the regime of parameters where the diblock copolymers exhibit lamellar morphologies, and study the alignment behavior of the lamellar morphologies on the grafted substrates. Our results reveal a templating of the self-assembly morpology by the brush chains. We find two novel features of this templating behavior: The ends of the grafted chains rearrange themselves to create a more favorable interface, an effect which is present in both the parallel and perpendicular morphologies, and is enhanced with increasing blockiness of the sequences of the random copolymer. In addition, the brush chains may splay laterally in perpendicular morphologies and enrich the interface even further in the favorable component. The latter feature leads to nontrivial free energy differences between the parallel and perpendicularly aligned lamellae on the grafted surface. We explicitly find the parametric window for the stability of perpendicular lamellae and compare against the trends suggested by surface energies of the pure homopolymeric components. Such comparisons indicate that viewing the grafted surface purely in terms of the surface energies of the components of the diblock copolymer may not necessarily capture the stabilities of the parallel and perpendicular morphologies.